Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to transferring a Voice-over-Long Term Evolution (VoLTE) call to a Universal Mobile Telecommunications System (UMTS) packet switched (PS) based voice based call.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the UMTS, a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
Generally, delivering a PS Handover based Voice-over-Internet Protocol (VoIP) over High Speed Packet Access (HSPA) from a VoLTE call without Quality-of-Service (QoS) implementation in the HSPA radio access network is challenging because of the need to sustain jitter/delay-sensitivity voice requirements. Thus, there is a need for transferring a VoLTE call to a UMTS (or an HSPA) PS based voice call with minimal reduction in voice traffic, thereby providing consistent service in a wireless communication system.